Welding Power PWM Linearization for Stable Low-Amperage Arcs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing welding type systems with PWM control experience instability and non-linear duty cycle oscillations at low output levels, leading to unstable arcs during low amperage operations.
Innovation Solution
A welding type system with a PWM module that includes a short duty cycle linearizing module and charging ramp module to adjust the PWM transfer function, ensuring a more linear relationship between duty cycle and command signal, even at shorter duty cycles below the PWM minimum on time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PWM control is used in welding type systems, then power regulation capability is improved, but stability deteriorates at low output levels due to non-linear duty cycle oscillations
Solution Approach 1:
The patent modifies the PWM transfer function parameters by introducing a linearizing module that adjusts the relationship between duty cycle and command signal. This changes the system parameters to maintain linearity at low duty cycles, preventing oscillations and improving arc stability while preserving power regulation capability across the full output range.
Solution Approach 2:
The patent introduces an intermediary linearizing module between the PWM controller and the power circuit. This intermediary component processes the command signal to compensate for non-linearities, ensuring stable arc control at low output levels while maintaining the benefits of PWM control for power regulation.
2Device complexity
If standard PWM transfer function is used, then control simplicity is maintained, but manufacturing precision deteriorates due to non-linear duty cycle relationship at short duty cycles
Solution Approach 1:
The patent changes the PWM transfer function parameters by implementing a linearizing module that adjusts the duty cycle-command signal relationship. This ensures consistent and precise control across the entire duty cycle range, including short duty cycles, without significantly increasing control circuit complexity.
Solution Approach 2:
The patent makes the PWM transfer function dynamic by adjusting its characteristics based on the duty cycle range. The linearizing module dynamically compensates for non-linearities, ensuring precise duty cycle control at all operating points while maintaining overall system simplicity.
3Reliability
If PWM minimum on time is increased, then switch reliability is improved, but productivity deteriorates due to reduced maximum output capability
Solution Approach 1:
The patent makes the switching frequency dynamic by allowing it to vary with the duty cycle. At low duty cycles, the frequency increases to accommodate the minimum on time requirement while maintaining maximum output capability. This dynamic adjustment ensures both switch reliability and full productivity across the operating range.
Solution Approach 2:
The patent changes the switching frequency parameter dynamically based on the duty cycle and minimum on time requirements. This parameter adjustment ensures that switches operate reliably at all duty cycles while maintaining the ability to deliver maximum output power when needed.
Data Source
AI summary
A method and apparatus for providing welding-type power includes an input circuit, a power circuit, and a controller. The input circuit receives input power and provides intermediate power. The power circuit has a power control input with at least one switch that responds to the control input. The power circuit receives the intermediate power and provides welding type output power. The controller has a set point input and a control output. The control output is connected to the power control input. The control circuit also includes a pwm module that responds to the user set point input and provided the control output. The pwm module can include a short duty cycle linearizing module. The pwm module can also include a short duty cycle charging ramp module.